Posts Tagged ‘cabbage’

While most vegetable growers finish up with fall crops around Thanksgiving, there is potential to produce throughout the fall and winter. There are fall and winter sales potentials with schools, institutions, and restaurants; for CSA’s; and for specialty wholesale markets.

One strategy is using storage to have products available out of season. This has been a common practice on a large wholesale scale with potatoes and apples where large controlled environment storage facilities are used. On a smaller scale, there are many vegetables that can be stored in sheds, cold boxes, or greenhouses as long as products are kept above freezing and have adequate humidity. It should be noted that critical minimum temperatures will vary according to the type of produce.

Probably the easiest vegetables to store are hard shelled winter squash such as butternuts. If kept around 50°F, most of the hard shelled squashes can be kept for at least 3 months, some for over 6 months. Potatoes store best at 45°F in high humidity and sprouting can be a problem for longer storage. Sweet potatoes, once cured, can be stored for months as long as the storage temperature is kept around 60°F. Colder temperatures damage the roots. Onion storage depends on the type but longest storage is just above freezing in dry conditions. Cabbage can also be stored for long periods. The key is to grow storage varieties that are dense. Longest storage is at 32 F° in high humidity. Napa type chinese cabbage also stores well in refrigeration (several months). Other crops successfully stored include carrots, parsnips, rutabegas, and turnips. In fruits, long keeping apple varieties can be stored for months in cool temperatures.

Field storage is another way to extend sales of some vegetables. Root crops such as carrots, parsnips, and beets can be kept for extended periods in the field if kept from freezing with row covers or straw mulch. Certain cabbage varieties can field store into winter if protected from hard freezes with row covers. Green onions and leeks also field store well.

An alternative strategy is to make used of high tunnels, low tunnels, row covers, or a combination to grow cool season crops for fall and winter harvest. Greens crops in the mustard family (mustard, turnip, kale, collard, cress, many asian greens); spinach, chard, and beet greens; and lettuces and endive can be planted in the late summer or fall and harvested repeatedly through the fall and winter in these protected systems without additional heat. Some day neutral strawberries can be harvested into the late fall in high tunnels or low tunnel/row cover systems. The use of row covers can also extend harvest periods for crops such as broccoli where side shoot production can be maintained after main heads are harvested, often through Christmas, and Brussels sprouts where sprout production can be extended into winter.

Of course, there is potential for production of many crops in heated greenhouses. The choice of varieties becomes important for greenhouse production because of the lower light and reduced daylength conditions in fall and winter. Specific greenhouse varieties of crops such as tomatoes, lettuce, and cucumbers have been developed for fall and winter production.

Long time growers of cole crops know that the micronutrient boron is critical for production. However, newer growers may be unaware of these requirements. Boron is also subject to leaching with rainfall, particularly in our sandy soils, so available soil boron declines over time.

Cole crops have a moderate to high boron requirement. Symptoms of boron deficiency vary with crop type. Most boron deficient cole crops develop cracked and corky stems, petioles and midribs. The stems of broccoli, cabbage and cauliflower can be hollow and are sometimes discolored. Cauliflower curds become brown and leaves may roll and curl, while cabbage heads may be small and yellow. Of all the cole crops, cauliflower is the most sensitive to boron deficiencies.

It is recommended in broccoli and kale to apply 1.5-3 pounds of boron (B) per acre in mixed fertilizer prior to planting. In Brussels sprouts, cabbage, collards and cauliflower, boron and molybdenum are recommended. Apply 1.5-3 pounds of boron (B) per acre and 0.2 pound molybdenum (Mo) applied as 0.5 pound sodium molybdate per acre with broadcast fertilizer.

Boron may also be applied as a foliar treatment to cole crops if soil applications were not made. The recommended rate is 0.2-0.3 lb/acre of actual boron (1.0 to 1.5 lbs of Solubor 20.5%) in sufficient water (30 or more gallons) for coverage. Apply foliar boron prior to heading of cole crops.

Other fall crops such as beets, radishes, and turnips are also susceptible to boron deficiencies in sandy soils with limited boron fertilizer additions.

Symptoms of downy mildew include purple to yellowish- brown spots on upper leaf surfaces. A grayish-white spore mass will develop and cover the underside of leaves under ideal temperatures (night temperatures of 46 – 61°F and day temperatures below 75°F. Downy mildew can kill young plants. Heavily infected leaves may drop providing entry points for bacterial infections (black rot and soft rot). Symptoms of Alternaria on infected leaves include small, expanding circular lesions with concentric rings that may have a ‘shot-hole’ appearance as lesions age. Heavily infected seedlings may result in damping-off. Control of Downy mildew and Alternaria begins with preventative fungicide applications. Use one of the following at the first sign of disease and continue every 7 to 10 days (Please refer to the pesticide table on page F21 of the 2011 DE Commercial Vegetable Production Recommendationsto determine which fungicide is labeled for each specific crop.):
● Quadris (azoxystrobin, 11) at 6.0 to 15.5 fl oz 2.08SC/A, or
● chlorothalonil (M5) at 1.5 pt 6F/A or OLF, or
● Cabrio (pyraclostrobin, 11) at 12.0 to 16.0 oz 20EG/A, or
● Endura (boscalid, 7) at 6.0 to 9.0 oz 70WG/A, or
● Ridomil Gold Bravo (mefenoxam + chlorothalonil, 4 + M5) at 1.5 lb 76.5WP/A (14-day schedule),
● Manzate Pro-Stick (mancozeb, M3) at 1.6 to 2.1 lb 75DF/A, or
● Switch (cyprodinil, 9) at 11.0 to 14.0 oz 62.5WG/A (Alternaria only).

For downy mildew only, apply either:
● Actigard (acibenzolar-S-methyl, P) at 1.0 oz 50WG/A (begin applications 7-10 days after thinning and re-apply every 7 days for a total of 4 applications per season.), or
● Aliette (fosletyl Al, 33) at 3.0 to 5.0 lb 80WDG/A (on 14-day schedule).

Plantings for fall harvested vegetables are underway. Timing these plantings can be a challenge, especially where multiple harvests are needed. Plantings from mid-July through the end of August may be made, with cutoff dates depending on the crop, variety, and season extension methods such as row covers, low tunnels, and high tunnels.

These plantings can be divided into 2 groups: 1) warm season vegetables for harvest up to a killing frost and 2) cool season vegetables for extended harvest in the fall.

The three main factors influencing crop growth and performance in the fall are daylength, heat units, and frost or freeze events. A few days difference in planting date this time of year can make a big difference in days to maturity in the fall.

Warm season vegetables for fall harvest include snap beans, squash, and cucumbers. July plantings of sweet corn can also be successful to extend seasons for farm stands. Mid-July plantings of tomatoes and peppers also are made for late harvests, particularly in high tunnels.

To extend harvest in the fall, successive plantings are an option. However, days between plantings will need to be compressed. One day difference in early August planting for a crop like beans can mean a difference of several days in harvest date.

Another option to extend harvest in the fall is with planting different maturing varieties at the same time. This is particularly successful with crops such as broccoli and cabbage where maturity differences of more than 30 days can be found between varieties.

Another way to get later harvests is by use of row covers or protecting structures. This can allow for more heat accumulation and will aid with protection against frost and freezes. Decisions on what type or combination of covers/protection to use and when to apply the protection will influence fall vegetable maturation and duration of harvest.

A final factor for summer planting for fall production is on planting cutoff dates. For example, a crop such as cucumber may produce well with an August 2 planting but poorly with an August 8 planting; broccoli has a wider planting window than cauliflower; turnip greens have a wider planting window than kale.

Bolting is the term used for flower stalk formation in vegetables. Bolting response may be related to temperature, daylength, or a combination.

Bolting in spinach, lettuce, and some radishes (oriental types) will occur naturally as days get longer. High temperatures will accelerate bolting in spinach and lettuce.

Many mustard family plants need a cold period along with lengthening days to flower. The amount of cold needed depends on the species and variety. Mustards are very prone to cold initiated spring bolting; turnips, Chinese cabbage, and salad radishes require more cold to initiate the bolting response.

In the cole crop group, cabbage planted very early in cold springs may bolt and premature flowering in broccoli, cauliflower, kale, and collards also occurs when planted too early, or if the spring is abnormally cold. However, cole crop transplants have to be of a certain age to be susceptible to this cold-initiated bolting.

Other biennial vegetables such as beets, carrots, and onions also can be induced to bolt but only once plants have reached a certain size (they are past the juvenile growth stage). This is uncommon in our region.

Controlling bolting starts with planting during the recommended planting window. Early planting will contribute to bolting in some crops (such as cabbage), late planting in others (such as lettuce).

Select varieties that are adapted to the spring planting season (an example would be Savannah mustard). Chose slow bolting varieties of spinach and lettuce. Choose spring adapted varieties of oriental radishes and Chinese cabbage.

One issue that complicates this is the use of high tunnels for early production. High tunnels allow for earlier planting but cold snaps still may drop temperatures enough to cause the cold induced flowering response in many of these crops.

Downy mildew and Alternaria can be a problem in fall crops (cabbage, collards, broccoli, cauliflower, and kale). When the disease first appears, apply a fungicide every 7 to 10 days. Quadris, chlorothalonil, Cabrio, Endura (Alternaria only), Ridomil Gold Bravo, or Switch (Alternaria only) and Actigard (Downy mildew only) and Aliette (Downy mildew only) are labeled for control. For more information on control please see the 2010 Delaware Commercial Vegetable Production Recommendations.

Cole crops, including cabbage, broccoli, cauliflower, Brussels sprouts, collards, kale, and kohlrabi are important fall crops in the region. The following are some common disorders that affect these crops and their causes.

Tipburn of Cauliflower, Cabbage, and Brussels Sprouts
This problem can cause severe economic losses. Tipburn is a breakdown of plant tissue inside the head of cabbage, individual sprouts in Brussels sprouts, and on the inner wrapper leaves of cauliflower. It is a physiological disorder which is associated with an inadequate supply of calcium in the affected leaves, causing a collapse of the tissue and death of the cells. Calcium deficiency may occur where the soil calcium is low or where there is an imbalance of nutrients in the soil along with certain weather conditions. (High humidity, low soil moisture, high potash and high nitrogen aggravate calcium availability). Secondary rot caused by bacteria can follow tipburn and heads of cauliflower can be severely affected. Some cabbage and cauliflower cultivars are relatively free of tipburn problems.

Boron Deficiencies
Cole crops have a high boron requirement. Symptoms of boron deficiency vary with the cole crop. Cabbage heads may simply be small and yellow. Most cole crops develop cracked and corky stems, petioles and midribs. The stems of broccoli, cabbage and cauliflower can be hollow and are sometimes discolored. Cauliflower curds become brown and leaves may roll and curl.

Hollow Stem in Broccoli and Cauliflower Not Caused by Boron Deficiency
This condition starts with gaps that develop in the tissues. These gradually enlarge to create a hollow stem. Ordinarily, there is no discoloration of the surface of these openings at harvest but both discoloration and tissue breakdown may develop soon after harvest. Some cultivars of hybrid cauliflower and broccoli may have openings from the stem into the head. Both plant spacing and the rate of nitrogen affect the incidence of hollow stem. Hollow stem increases with wider spacings and as the rate of nitrogen increases. The incidence of hollow stem can be greatly reduced by increasing the plant population.

Cabbage Splitting
Cabbage splitting is mainly a problem with early cabbage. A problem can develop when moisture stress is followed by heavy rain. The rapid growth rate associated with rain, high temperatures and high fertility cause the splitting. Proper irrigation may help prevent splitting and there are significant differences between cultivars in their susceptibility to this problem. Splitting may also be partially avoided by deep cultivation to break some of the plant roots.

Cauliflower and Broccoli Buttoning
Buttoning is the premature formation of a head and because the head forms early in the plant’s life, the leaves are not large enough to nourish the curd to a marketable size. Buttoning may occur shortly after planting in the field, when normal plants of the same age should be growing vegetatively. Losses are usually most severe when transplants have gone past the juvenile stage before setting in the field. Stress factors such as low soil nitrogen, low soil moisture, disease, insects, or micronutrient deficiencies can also cause this problem. Some cultivars, particularly early ones, are more susceptible to buttoning than others.

Lack of Heads in Broccoli and Cauliflower
During periods of extremely warm weather (days over 86°F and nights 77°F) broccoli and cauliflower can remain vegetative (does not head) since they do not receive enough cold for head formation. This can cause a problem in scheduling the marketing of even volumes of crop.

Cauliflower Blanching and Off Colors
The market demands cauliflower which is pure white or pale cream in color. Heads exposed to sunlight develop a yellow and/or red to purple pigment. Certain varieties such as Snow Crown are more susceptible to purple off-colors, especially in hot weather. Self-blanching varieties have been developed to reduce problems with curd yellowing. For open headed varieties, the usual method to exclude light is to tie the outer leaves when the curd is 8 cm in diameter. Leaves may also be broken over the curd to prevent yellowing. In hot weather blanching may take 3 to 4 days, but in cool weather, 8 to 12 days or more may be required. Cauliflower fields scheduled to mature in cool weather (September and October) that are well supplied with water and planted with “self-blanching” cultivars will not need tieing. Newer orange cauliflower and green broccoflower varieties are being planted. They are less susceptible to off-colors but still can develop purpling under warm conditions.

Cauliflower Ricing
“Riciness” and “fuzziness” in heads is caused by high temperatures, exposure to direct sun, too rapid growth after the head is formed, high humidity, or high nitrogen. “Ricing” is where the flower buds develop, elongate and separate, making the curd unmarketable.

Development of Curd Bracts in Cauliflower
Curd bracts or small green leaves between the segments of the curd in cauliflower is caused by too high of temperature or drought. High temperatures cause a reversion to vegetative growth with production of bracts on the head. In a marketable cauliflower head, the individual flower buds are undeveloped and undifferentiated.

Loose Heads in Cauliflower and Premature Flowering in Broccoli
Loosely formed curds in cauliflower can be due to any stress that slows growth making them small or open. Fluctuating temperatures and moisture will also cause less compact growth. In contrast, excess vegetative growth caused by excessive nitrogen can also cause loose heads in cauliflower and broccoli. Premature flowering and open heads in broccoli can be brought on by high temperatures.

Edema on Cole Crop Leaves
Edema is water blistering on cole crop leaves. The most common cause of edema is the presence of abundant, warm soil water and a cool, moist atmosphere. Under these conditions the roots absorb water at a rate faster than is lost through transpiration. Excess water accumulates in the leaf, some parenchyma cells enlarge and block the stomatal openings through which water vapor is normally released from the plant; thereby contributing to further water retention in the leaf. If this condition persists, the enlarged cells divide, differentiate a cork cambium, and develop elongate cork cells externally to form a periderm. The rupture of the epidermis by the enlarged inner cells and the periderm account for the raised, crusty appearance of older edema spots.

Black Petiole
Black petiole or black midrib is an internal disorder of cabbage that has been occasionally noted in recent years. As heads approach maturity, the back side of the internal leaf petioles or midribs turn dark gray or black at or near the point where the midrib attaches to the core. The affected area may be quite limited or may extend for 2 or 3 inches along the midrib. It is believed that this disorder is associated with a potassium (K)-phosphorus (P) imbalance and results when the K level in the soil is low and the P concentration high. High rates of nitrogen may contribute to the problem. Probably, as in the case with tipburn, black petiole is a complex physiological disorder in which environmental conditions play an important role in symptom expression. Variety evaluation trials have shown that there are differences in degree of susceptibility between varieties.

Floret (Bead) Yellowing in Broccoli
The florets are the most perishable part of the broccoli head; yellowing may be due to overmaturity at harvest, high storage temperatures after harvest, and/or exposure to ethylene. Any development of yellow beads ends commercial marketability. Bead yellowing due to senescence should not be confused with the yellow to light-green color of areas of florets not exposed to light during growth, sometimes called “marginal yellowing”.

Brown Floret (Bead) in Broccoli
This is a disorder in which areas of florets do not develop correctly, die and lead to brown discolored areas. This is thought to be caused by plant nutritional imbalances but also may be due to feeding damage on florets from insects such as harlequin bugs.

Lima BeansContinue to scout for downy mildew. The recent weather is very favorable for downy mildew. If downy is found apply RidomilGold/Copper, Phostrol or other labeled phosphorus acid (phosphonate) fungicide. If disease has not appeared in the field Headline, Forum or fixed copper fungicide can be applied preventatively in addition to Ridomil Gold/Copper and phosphorus acid fungicides.

Sweet CornField corn is not the only host for the fungus that caused Northern corn leaf blight. I have seen several fields of sweet corn recently with very high levels of infection clear to the top of the plant. Ears from badly infected plants were not filled out and will not be worth harvesting. Northern has been favored by the cooler and wetter season.

Tomatoes
Late blight is resurging on backyard tomato plantings at the present time. There is nothing besides chlorothalonil and mancozeb for homeowners but late season commercial planting should be protected from late blight with any of the late blight specific fungicides.

Cole Crops
Downy mildew and Alternaria can be a problem in fall cole crops (cabbage, collards, broccoli, cauliflower, and kale). When the disease first appears apply a fungicide every 7 to 10 days. Quadris, chlorothalonil, Cabrio, Endura (Alternaria only) Maneb, Ridomil Gold Bravo, Switch (Alternaria only), Actigard (downy mildew only) and Aliette (downy mildew only) are labeled for control. For more information on control please see the 2009 Delaware Commercial Vegetable Production Recommendations.

Symptoms of Alternaria on infected leaves include small, expanding circular lesions with concentric rings that may have a ‘shot-hole’ appearance as lesions age. Heavily infected seedlings may result in damping-off.

Control of downy mildew and Alternaria begins with preventative fungicide applications. Use one of the following at the first sign of disease and continue every 7 to 10 days: (Please refer to the pesticide table on page F21 of the 2009 Delaware Commercial Vegetable Production Recommendationsto determine which fungicide is labeled for each specific crop.)
● Quadris (azoxystrobin, 11) at 6.0 to 15.5 fl oz 2.08F/A
● chlorothalonil (M5) at 1.5 pt 6F/A or OLF
● Cabrio (pyraclostrobin, 11) at 12.0 to 16.0 oz 20EG/A
● Endura (boscalid, 7) at 6.0 to 9.0 oz 70WG/A
● maneb (M3) at 1.5 to 2.0 lb 75DF/A or OLF
● Ridomil Gold Bravo (mefenoxam + chlorothalonil, 4 + M5) at 1.5 lb 76.5WP/A (14-day schedule)

For downy mildew only, apply:
Actigard (acibenzolar-S-methyl, P1) at 1.0 oz 50WG/A (Begin applications 7-10 days after thinning and re-apply every 7 days for a total of 4 applications per season.)or
Aliette (fosetyl Al, 33) at 3.0 to 5.0 lb 80WDG/A (on a 14-day schedule).

Lima Beans
Ridomil Gold/Copper is now labeled nationally for control of downy mildew on lima beans. A 24c label is no longer needed for DE and MD.

Fungi-Phite is a phosphorus acid salt fungicide similar to Phostrol and is now labeled for downy mildew on lima beans. I have had this product in my tests for two years and it has performed extremely well, comparable to Ridomil/Gold Copper and Phostrol. Availability may be limited. It is not listed in the 2009 Commercial Vegetable Recs.

Cantaloupe and Watermelon
Quintec 2.08SC from Dow AgroSciences was labeled during last season and is a good powdery mildew fungicide in a new FRAC group 13 that can be alternated with Rally or Procure in addition to Pristine.

BravoThe Bravo label has been expanded to include peppers (bell pepper, chili pepper, cooking pepper, pimento, sweet pepper), gourds, eggplant, okra, rhubarb, and cabbage. These new changes are not in the 2009 Commercial Vegetable Recs. With the phasing out of maneb these Bravo additions will replace many of the maneb applications on these crops that might be grown in DE.